Nonclassical Phase Space Jumps and Optimal Spawning
Significant attempts have been made toward the intuitive understanding of nonclassical Franck-Condon factors that govern many important molecular processes from radiationless transitions to electronic spectroscopy. In the classical picture, i.e., Condon approximation, nuclear motion is assumed frozen throughout the duration of electronic transitions. However, as is demonstrated in this chapter, position and momentum jumps can compete in determining the Franck-Condon factor such that the conventional propensity rule can be misleading. We present a new method in this chapter where both position and momenta are simultaneously altered to achieve an improved description of nonadiabatic events. This optimal spawning procedure reduces to simpler approaches such as the strict momentum jump in appropriate limits, but is sufficiently flexible to describe cases where both position and momentum adjustments are important.